The answer is very simple here. It is normal to see fluctuations in SERPs(the search engine results pages). There are continuous changes in in SERPs and your competitors are also optimizing their web sites as well. So it is normal to rank number one and then number three and then number five, and then go back to number two. These are normal changes.

My advice would be to just focus on your audience and build quality content, compelling content and unique content that is tailored for your users exactly.